J. Kissel

Last week, I was alarmed to find that the ETMY ESD's angular effective bias voltage had shot up ~30-40 [V] (see LHO aLOG 37628) since we last measured it on June 27th, prior to the Montana EQ (on July 6th 2017, UTC, LHO aLOG 37344).

We've since resumed regularly measuring the charge, and delightfully, it looks like ETMY is on its way back down towards zero effective bias voltage. As always, we need about ~1 months worth of data to really make a statement about the trend, but this is encouraging. My guess is that the recent poor duty cycle has given ETMY lots of time with the opposite-from-nominal requested bias voltage, thus discharging the system. This will take some time though. 

The longitudinal actuation strength does not appear to have changed, still hovering around 5-6% decrease in strength from January 2017 (which is compensated for with kappa_tst as shown in the fifth attachment).

ETMX still looks under control, with effective bias voltage for most quadrants around 30 [V]. 

We'll continue to keep a close eye on this, and potentially measure Thursday / Friday if there's another opportune (less destructive) EQ or other down time.